delwinv

A very tiny plugin that adds the ACF field key, field name, Flexible Content field name and Flexible Content layout name to the WYSIWYG 
editor body tag, allowing you to target these classes, along with the existing post-type-* classes added by default by WordPress, in 
your editor-style.css for a better admin/editor experience.
This works for both ACF and ACF Pro, version 5.
<h3>Usage</h3>
<ol>
<li>Install the plugin through the Install Plugins interface or by uploading the <code>acf-plugin-wysiwyg-styling</code> folder to your <code>/wp-content/plugins/</code> directory.</li>
<li>Activate the ACF WYSIWYG Styling plugin from the Admin > Plugins menu.</li>
<li>Create or edit your editor-style.css in your theme directory and use the newly added classes to style your WYSIWYG editors.</li>
</ol>
For example:
<ul>
<li>
The ACF WYSIWYG field with key field_9999ffff11112222 can be targeted with the following CSS:
body.acf-field-key-field_9999ffff11112222 { 
 background-color: red; 
}
</li>
<li>
The ACF WYSIWYG field with key field_9999ffff11112222 in the “room” post type can be targeted with the following CSS:
body.post-type-room.acf-field-key-field_9999ffff11112222 { 
 background-color: blue; 
}
</li>
<li>
All ACF WYSIWYG fields named “my_wysiwyg” can be targetted with the following CSS:
body.acf-field-name-my_wysiwyg { 
 background-color: yellow; 
}
</li>
<li>
All ACF WYSIWYG fields in the Flexible Content field named “page_content” can be targetted with the following CSS:
body.acf-flex-name-page_content { 
 color: green; 
}
</li>
<li>
All ACF WYSIWYG fields in the Flexible Content layout field named “test_layout” can be targetted with the following CSS:
body.acf-layout-test_layout { 
 font-family: “Computer Modern Serif”; 
}
</li>
<li>
The ACF WYSIWYG field named “my_wysiwyg” in the Flexible Content layout field named “test_layout” can be targetted with the following CSS:
body.acf-layout-test_layout.acf-field-name-my_wysiwyg { 
 border: 4px solid red; 
 height: 100%; 
 margin: 0 auto; 
 max-width: 100px; 
}
</li>
</ul>
N.B. I target using the body tag so that a user cannot accidentally target the admin CSS in their edit of the field (regardless of how unlikely 
that would be).

ACF WYSIWYG Styling

Provides the necessary CSS classes in ACF WYSYWIG editor to allow for complete styling of the admin interface.

Peter Raschendorfer

The Smart CSS Auto Loader Plugin allows you to load additional CSS files without the need to change the theme
<h3>Retired Plugin</h3>
Development, maintenance and support of this plugin has been retired in october 2023. You can use this plugin as long as is works for you.
There will be no more updates and I won’t answer any support questions. Thanks for your understanding.
Feel free to fork this plugin.
<h3>Usage</h3>
To load additional stylesheets just put them into a directory named cssautoload (case-sensitive!). This directory can be placed in three different locations that are loaded in the following order:
<ul>
<li>Theme independent : in the <code>wp-content</code> directory</li>
<li>Theme dependent : in the Theme’s directory</li>
<li>Child Theme dependent (if using a Child Theme) : in the Child Theme’s directory</li>
</ul>
Only files with extension .css are added, all other files are ignored. Also files beginning with an underscore (_) are ignored.
<h3>CSS for different media</h3>
CSS allows to have different styles for different target devices. Files placed directly in the <code>cssautoload</code> directory are added with the media type ‘all’, suitable for all devices. To use a different media type just create a subdirectory with the name of the target media type (case-sensitive!). Te following CSS media types are supported according to the official CSS standard:
<ul>
<li><code>all</code> for all devices – you don’t need to create the <code>all</code> directory, you also can put the files directly into the cssautoload root directory</li>
<li><code>braille</code> for braille tactile feedback devices</li>
<li><code>embossed</code> for paged braille printers</li>
<li><code>handheld</code> for handheld devices</li>
<li><code>print</code> for printouts or print preview on screen</li>
<li><code>projection</code> for projected presentations</li>
<li><code>screen</code> for screens</li>
<li><code>speech</code> for speech synthesizers</li>
<li><code>tty</code> for media using a fixed-pitch character grid</li>
<li><code>tv</code> for television-type devices</li>
</ul>
Other subdirectories in <code>cssautoload</code> directory are ignored. Also subdirectories in the media subdirectories are not supported.
<h3>Plugin Privacy Information</h3>
<ul>
<li>This plugin does not set cookies</li>
<li>This plugin does not collect or store any data</li>
<li>This plugin does not send any data to external servers</li>
</ul>

ACF WYSIWYG Styling vs Smart CSS Auto Loader